1. Field of the Invention
The present invention relates to a hybrid integrated circuit module containing a hybrid integrated circuit, and more particularly to a hybrid integrated circuit module having high reliability, well suited for mass production, and inexpensive to manufacture.
2. Description of the Related Art
In recent years, various types of hybrid integrated circuits have been developed and commercialized for applications ranging from low-frequency to microwave ranges, as can be found in 50 MHz to 1000 MHz bands CATV amplifiers, portable 800 MHz to 1000 MHz band telephone transmitter amplifiers, 1 GHz or higher microwave amplifiers, etc.
To achieve general use of such hybrid integrated circuits, it is imperative to improve the reliability of the hybrid integrated circuit modules in which the hybrid integrated circuits are contained.
According to prior art hybrid integrated circuit modules, such as the one disclosed in U.S. Pat. No. 4,965,526, an alumina substrate is used as the hybrid integrated circuit substrate, on which semiconductor devices, such as Si transistors or GaAs FETs, chip resistors, thin-film resistors, chip capacitors, chip inductors, transformers, etc. are mounted.
Further, for enhanced reliability, the entire hybrid integrated circuit is covered with plastic, which is then sealed with a resin.
Furthermore, in the prior art hybrid integrated circuit module, electrodes, on which circuit components are soldered, are formed in the shapes that match the shapes of the individual circuit components.
Using an alumina substrate for the substrate of the hybrid integrated circuit, as in the prior art, is surely advantageous for mounting of circuit components that can generate heat, because the alumina substrate is a good thermal conductor.
However, not only is the alumina substrate itself expensive, but the interconnection pattern has to be formed by gold plating, since chip components such as a chip transistor cannot be mounted without gold plating on the alumina substrate. The gold plating causes the hybrid integrated circuit module to be expensive to manufacture. Another problem in using the alumina substrate is that the high thermal conductivity of the alumina substrate impairs the solderability of the circuit components and, accordingly, mass production efficiency is lost.
To resolve these problems, the hybrid integrated circuit substrate can be constructed using a glass-epoxy-based material that is inexpensive and that has low thermal conductivity. Implementing this, however, requires a design that can effectively cope with the heat that the circuit components generate.
Furthermore, the construction that involves covering the entire hybrid integrated circuit with plastic and sealing it with a resin, as in the prior art, has the problem of degradation of semiconductor device reliability in the long term because of insufficient hermeticity, since plastic has a low resistance to moisture.
Moreover, the construction that involves forming the electrodes, to which the circuit components are attached, in the shapes that match the shapes of the individual circuit components, as in the prior art, has the problem that mass production efficiency is reduced since, of the circuit components, chip components are the most difficult to remove.
That is, when it becomes necessary to replace a resistance-adjusting chip component, etc. after mounting because it does not provides the prescribed resistance value, etc., for example, the mounting portions of the chip component are heated and unsoldered using a soldering iron. The problem here is that heating the two ends at the same time is not an easy job, hence the difficulty in removing the chip component.
In such cases, previous methods for removing the chip component have been by heating the two portions at the same time by using two soldering irons or a special soldering iron having a bifurcated soldering head.